U.S. patent application number 11/054128 was filed with the patent office on 2005-06-30 for multi-chamber carrier head with a flexible membrane.
This patent application is currently assigned to Applied Materials, Inc., a California corporation. Invention is credited to Chen, Hung Chih, Zuniga, Steven M..
Application Number | 20050142993 11/054128 |
Document ID | / |
Family ID | 26915051 |
Filed Date | 2005-06-30 |
United States Patent
Application |
20050142993 |
Kind Code |
A1 |
Chen, Hung Chih ; et
al. |
June 30, 2005 |
Multi-chamber carrier head with a flexible membrane
Abstract
A carrier head that has a base assembly and a flexible membrane.
The flexible membrane has a generally circular main portion with a
lower surface that provides a substrate-mounting surface and a
plurality of concentric annular portions extending from the main
portion and secured to the base assembly. The volume between the
base assembly and the flexible membrane forming a plurality of
pressurizable chambers.
Inventors: |
Chen, Hung Chih; (San Jose,
CA) ; Zuniga, Steven M.; (Soquel, CA) |
Correspondence
Address: |
Patent Counsel
Applied Materials, Inc.
Legal Affairs Department
P.O. Box 450A
Santa Clara
CA
95052
US
|
Assignee: |
Applied Materials, Inc., a
California corporation
|
Family ID: |
26915051 |
Appl. No.: |
11/054128 |
Filed: |
February 8, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11054128 |
Feb 8, 2005 |
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09712389 |
Nov 13, 2000 |
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6857945 |
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60220641 |
Jul 25, 2000 |
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Current U.S.
Class: |
451/287 |
Current CPC
Class: |
B24B 37/30 20130101;
B24B 41/061 20130101; B24B 49/16 20130101 |
Class at
Publication: |
451/287 |
International
Class: |
B24B 029/00 |
Claims
What is claimed is:
1. A carrier head, comprising: a base assembly; and a flexible
membrane having a generally circular main portion with a lower
surface that provides a substrate-mounting surface and a plurality
of concentric flexible annular flaps secured to the base assembly,
the volume between the base assembly and the flexible membrane
forming a plurality of pressurizable chambers; wherein at least one
of the annular flaps is configured to reduce downward load
transmitted from at least one of the chambers through the annular
flap of the flexible membrane to the main portion so as to reduce
compressions in the main portion.
2. The carrier head of claim 1, wherein the annular flap includes a
notch.
3. The carrier head of claim 2 wherein the notch is formed at a
juncture between the at least one annular flap and the main
portion.
4. The carrier head of claim 1 wherein at least one of the annular
flaps includes a widened section adjacent a juncture between the at
least one annular flap and the main portion.
5. The carrier head of claim 4, wherein the at least one annular
flap includes a horizontal portion extending from the base assembly
to the widened section.
6. A carrier head, comprising: a base assembly; and a flexible
membrane having a generally circular main portion with a lower
surface that provides a substrate-mounting surface and a plurality
of concentric annular portions extending from the main portion and
secured to the base assembly, the volume between the base assembly
and the flexible membrane forming a plurality of pressurizable
chambers, and a means for reducing downward load transmitted from
at least one of the chambers through at least one of the annular
portions of the flexible membrane to the main portion so as to
reduce compressions in the main portion.
7. The carrier head of claim 6 wherein the means for reducing
download load comprises at least one of the annular portions
including a notch; wherein a first notch of the plurality of
notches is formed at a juncture between the at least one annular
portion and the main portion and a second notch of the plurality of
notches is formed at about a mid-point of the annular portion.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Under 35 U.S.C. .sctn.1.20, this application is a
continuation of and claims priority to U.S. application Ser. No.
09/712,389, filed on Nov. 13, 2000, which claims priority to U.S.
Provisional Application Ser. No. 60/220,641, filed Jul. 25, 2000.
The disclosure of the prior applications are considered part of and
are incorporated by reference in the disclosure of this
application.
BACKGROUND
[0002] The present invention relates generally to chemical
mechanical polishing of substrates, and more particularly to a
carrier head for use in chemical mechanical polishing.
[0003] An integrated circuit is typically formed on a substrate by
the sequential deposition of conductive, semiconductive or
insulative layers on a silicon wafer. One fabrication step involves
depositing a filler layer over a non-planar surface, and
planarizing the filler layer until the non-planar surface is
exposed. For example, a conductive filler layer can be deposited on
a patterned insulative layer to fill the trenches or holes in the
insulative layer. The filler layer is then polished until the
raised pattern of the insulative layer is exposed. After
planarization, the portions of the conductive layer remaining
between the raised pattern of the insulative layer form vias, plugs
and lines that provide conductive paths between thin film circuits
on the substrate. In addition, planarization is needed to planarize
the substrate surface for photolithography.
[0004] Chemical mechanical polishing (CMP) is one accepted method
of planarization. This planarization method typically requires that
the substrate be mounted on a carrier or polishing head. The
exposed surface of the substrate is placed against a rotating
polishing disk pad or belt pad. The polishing pad can be either a
"standard" pad or a fixed-abrasive pad. A standard pad has a
durable roughened surface, whereas a fixed-abrasive pad has
abrasive particles held in a containment media. The carrier head
provides a controllable load on the substrate to push it against
the polishing pad. A polishing slurry, including at least one
chemically-reactive agent, and abrasive particles if a standard pad
is used, is supplied to the surface of the polishing pad.
SUMMARY
[0005] In one aspect, the invention is directed to a carrier head
that has a housing to be secured to a drive shaft, a base assembly,
a loading chamber controlling the position of the base assembly
relative to the housing, and a flexible membrane. The flexible
membrane has a generally circular main portion with a lower surface
that provides a substrate-mounting surface and a plurality of
concentric annular flaps secured to the base assembly. The volume
between the base assembly and the flexible membrane forms a
plurality of pressurizable chambers.
[0006] Implementations of the invention may include one or more of
the following features. A retaining ring may be joined to the base
assembly. The carrier head may include five pressurizable chambers.
Each chamber may control a downward pressure by an associated
segment of the main portion of the flexible membrane on a
substrate. At least one of the annular flaps may include a notch.
The notch may be formed at a juncture between the at least one
annular flap and the main portion. At least one of the annular
flaps may include a widened section adjacent a juncture between the
at least one annular flap and the main portion. The at least one
annular flap may includes a horizontal portion extending from the
base assembly to the widened section.
[0007] In another aspect, the invention is directed to a carrier
head that has a base assembly and a flexible membrane. The flexible
membrane has a generally circular main portion with a lower surface
that provides a substrate-mounting surface and a plurality of
concentric annular portions extending from the main portion and
secured to the base assembly. The volume between the base assembly
and the flexible membrane forms a plurality of pressurizable
chambers.
[0008] In another aspect, the invention is directed to a method of
sensing the presence of a substrate. A first chamber of a plurality
of chambers in a carrier head is evacuated. The carrier head
includes a base assembly and a flexible membrane main portion with
a lower surface that provides a substrate-mounting surface and a
plurality of concentric annular portions extending from the main
portion and secured to a base assembly of a carrier head. The
volume between the base assembly and the flexible membrane forms
the plurality of pressurizable chambers. A pressure in second one
of the plurality of chambers is measured, and whether the substrate
is attached to the substrate-mounting surface is determined from
the measured pressure.
[0009] Implementations of the invention may include one or more of
the following features. Determining whether the substrate is
attached to the substrate-mounting surface may include comparing
the measured pressure to a threshold. The substrate may be
determined to be present if the measured pressure is greater than
the threshold.
[0010] Implementations of the invention may include one or more of
the following features. Determining whether the substrate is
attached to the substrate-mounting surface may include comparing
the measured pressure to a threshold. The substrate may be
determined to be present if the measured pressure is greater than
the threshold.
[0011] In another aspect, the invention is directed to a carrier
head with a base assembly and a flexible membrane. The flexible
membrane has a plurality of concentric annular portions extending
from the main portion and secured to the base assembly, at least
one of which includes a notch. The flexible membrane has a
generally circular main portion with a lower surface that provides
a substrate-mounting surface. The volume between the base assembly
and the flexible membrane forms a plurality of pressurizable
chambers.
[0012] Implementations of the invention may include one or more of
the following features. The notch may be formed at a juncture
between the at least one annular portion and the main portion. The
at least one annular portion may include a plurality of notches. A
first notch of the plurality of notches may be formed at a juncture
between the at least one annular portion and the main portion, and
a second notch of the plurality of notches may be formed at about a
mid-point of the annular portion.
[0013] In another aspect, the invention is directed to a carrier
head with a base assembly and a flexible membrane. The flexible
membrane has a generally circular main portion, an outer annular
portion, and an inner annular portion that includes a notch. The
main portion has a lower surface that provides a substrate-mounting
surface. The outer annular portion extends from an edge of the main
portion and secured to the base assembly. The an inner annular
portion extends from the main portion and is secured to the base
assembly, the volume between the base assembly and the flexible
membrane forming a plurality of pressurizable chambers.
[0014] In another aspect, the invention is directed to a carrier
head that has a base assembly and a flexible membrane. The flexible
membrane has a generally circular main portion, an outer annular
portion, and an inner annular portion that includes a widened
section adjacent a juncture between the inner annular portion and
the main portion. The main portion has a lower surface that
provides a substrate-mounting surface. The outer annular portion
extends from an edge of the main portion and is secured to the base
assembly. The inner annular portion extends from the main portion
is secured to the base assembly, the volume between the base
assembly and the flexible membrane forming a plurality of
pressurizable chambers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a cross-sectional view of a carrier head according
to the present invention.
[0016] FIG. 2 is an enlarged view of a carrier head illustrating a
flexible membrane with a notch in each flap.
[0017] FIG. 3 is an enlarged view of a carrier head illustrating a
flexible membrane with a multiple notches in each flap.
[0018] FIG. 4A is an enlarged view of a carrier head illustrating a
flexible membrane with wide connection between each flap and the
base portion of the membrane.
[0019] FIG. 4B is a view of the carrier head of FIG. 4A
illustrating the motion of an outer portion of the flexible
membrane.
DETAILED DESCRIPTION
[0020] Referring to FIG. 1, the carrier head 100 includes a housing
102, a base assembly 104, a gimbal mechanism 106 (which may be
considered part of the base assembly), a loading chamber 108, a
retaining ring 110, and a substrate backing assembly 112 which
includes five pressurizable chambers. A description of a similar
carrier head may be found in U.S. patent application Ser. No.
08/861,260, filed May 21, 1997, the entire disclosure of which is
incorporated herein by reference.
[0021] The housing 102 can generally circular in shape and can be
connected to the drive shaft 74 to rotate therewith during
polishing. A vertical bore 120 may be formed through the housing
102, and five additional passages 122 (only two passages are
illustrated) may extend through the housing 102 for pneumatic
control of the carrier head. O-rings 124 may be used to form
fluid-tight seals between the passages through the housing and
passages through the drive shaft.
[0022] The base assembly 104 is a vertically movable assembly
located beneath the housing 102. The base assembly 104 includes a
generally rigid annular body 130, an outer clamp ring 134, and the
gimbal mechanism 106. The gimbal mechanism 106 includes a gimbal
rod 136 which slides vertically the along bore 120 to provide
vertical motion of the base assembly 104, and a flexure ring 138
which bends to permit the base assembly to pivot with respect to
the housing 102 so that the retaining ring 110 may remain
substantially parallel with the surface of the polishing pad.
[0023] The loading chamber 108 is located between the housing 102
and the base assembly 104 to apply a load, i.e., a downward
pressure or weight, to the base assembly 104. The vertical position
of the base assembly 104 relative to the polishing pad 32 is also
controlled by the loading chamber 108. An inner edge of a generally
ring-shaped rolling diaphragm 126 may be clamped to the housing 102
by an inner clamp ring 128. An outer edge of the rolling diaphragm
126 may be clamped to the base assembly 104 by the outer clamp ring
134.
[0024] The retaining ring 110 may be a generally annular ring
secured at the outer edge of the base assembly 104. When fluid is
pumped into the loading chamber 108 and the base assembly 104 is
pushed downwardly, the retaining ring 110 is also pushed downwardly
to apply a load to the polishing pad 32. A bottom surface 116 of
the retaining ring 110 may be substantially flat, or it may have a
plurality of channels to facilitate transport of slurry from
outside the retaining ring to the substrate. An inner surface 118
of the retaining ring 110 engages the substrate to prevent it from
escaping from beneath the carrier head.
[0025] The substrate backing assembly 112 includes a flexible
membrane 140 with a generally flat main portion 142 and five
concentric annular flaps 150, 152, 154, 156, and 158 extending from
the main portion 142. The edge of the outermost flap 158 is clamped
between the base assembly 104 and a first clamp ring 146. Two other
flaps 150, 152 are clamped to the base assembly 104 by a second
clamp ring 147, and the remaining two flaps 154 and 156 are clamped
to the base assembly 104 by a third clamp ring 148. A lower surface
144 of the main portion 142 provides a mounting surface for the
substrate 10.
[0026] The volume between the base assembly 104 and the internal
membrane 150 that is sealed by the first flap 150 provides a first
circular pressurizable chamber 160. The volume between the base
assembly 104 and the internal membrane 150 that is sealed between
the first flap 150 and the second flap 152 provides a second
pressurizable annular chamber 162 surrounding the first chamber
160. Similarly, the volume between the second flap 152 and the
third flap 154 provides a third pressurizable chamber 164, the
volume between the third flap 154 and the fourth flap 156 provides
a fourth pressurizable chamber 166, and the volume between the
fourth flap 156 and the fifth flap 158 provides a fifth
pressurizable chamber 168. As illustrated, the outermost chamber
168 is the narrowest chamber. In fact, the chambers 152, 154, 156
and 158 can be configured to be successively narrower.
[0027] Each chamber can be fluidly coupled by passages through the
base assembly 104 and housing 102 to an associated pressure source,
such as a pump or pressure or vacuum line. One or more passages
from the base assembly 104 can be linked to passages in the housing
by flexible tubing that extends inside the loading chamber 108 or
outside the carrier head. Thus, pressurization of each chamber, and
the force applied by the associated segment of the main portion 142
of the flexible membrane 140 on the substrate, can be independently
controlled. This permits different pressures to be applied to
different radial regions of the substrate during polishing, thereby
compensating for non-uniform polishing rates caused by other
factors or for non-uniform thickness of the incoming substrate.
[0028] To vacuum chuck the substrate, one chamber, e.g., the
outermost chamber 168, is pressurized to force the associated
segment of the flexible membrane 140 against the substrate 10 to
form a seal. Then one or more of the other chambers located
radially inside the pressurized chamber, e.g., the fourth chamber
166 or the second chamber 162, are evacuated, causing the
associated segments of the flexible membrane 140 to bow inwardly.
The resulting low-pressure pocket between the flexible membrane 140
and the substrate 10 vacuum-chucks the substrate 10 to the carrier
head 100, while the seal formed by pressurization of the outer
chamber 168 prevents ambient air from entering the low-pressure
pocket.
[0029] Since it is possible for the vacuum-chucking procedure to
fail, it is desirable to determine whether the substrate is
actually attached to the carrier head. To determine whether the
substrate is attached to the flexible membrane, the fluid control
line to one of the chambers, e.g., the third chamber 164, is closed
so that the chamber is separated from the pressure or vacuum
source. The pressure in the chamber is measured after the
vacuum-chucking procedure by a pressure gauge connected to the
fluid control line. If the substrate is present, it should be drawn
upwardly when the chamber 162 is evacuated, thereby compressing the
third chamber 164 and causing the pressure in the third chamber to
rise. On the other hand, if the substrate is not present, the
pressure in the third chamber 164 should remain relative stable (it
may still increase, but not as much as if the substrate were
present). A general purpose computer connected to the pressure
gauge can be programmed to use the pressure measurements to
determine whether the substrate is attached to the carrier head.
The chambers that are not used for sealing, vacuum-chucking or
pressure sensing can be vented to ambient pressure.
[0030] Referring to FIG. 2, in one implementation, a notch or
indentation 200 is formed in each of the annular flaps 150a, 152a,
154a, and 156a, except the outermost flap 158, of the flexible
membrane 140a (flaps 150a is not shown in FIG. 2). Specifically,
each notch 200 can be formed as an annular recess located
immediately adjacent the main portion 142 of the flexible membrane
140a. Thus, the flaps 150a, 152a, 154a and 156a narrow (e.g., by a
factor of about two) at the connection 202 to the main portion 142
of the flexible membrane 140a. For example, the thickness T.sub.1
of the vertically extending portion 204 of the flap 154a may be
about 1 mm, and the thickness T.sub.2 of the flap 154a at the
connection 202 may be about 0.5 mm. Each notch 200 can be formed on
the same side of the flap as the rim 206 that is secured between
the associated clamp ring and the base.
[0031] A potential advantage of the notches is to improve polishing
uniformity when there is unequal pressure in adjacent chambers.
Specifically, when there is unequal pressure in adjacent chambers,
the pressure in the high pressure chamber tends to bow the
separating flap into the low pressure chamber. For example, bending
of the flap 150a at the connection 202 can lead to regions of
compression in the main portion 142 adjacent the central flap 150a,
resulting in an unintended pressure distribution and non-uniform
polishing. However, the notch 200 makes the flap 150a more flexible
at the connection 202. This reduces compression in the main portion
142 when the flap bends due to unequal pressure in chambers 160 and
162, thereby improving polishing uniformity.
[0032] Referring to FIG. 3, in another implementation, each of the
annular flaps 150b, 152b, 154b and 156b, includes three notches or
indentations 210, 212 and 214. The first notch 210 is formed
immediately adjacent the main portion 142 of the flexible membrane
140b, the second notch 212 is formed at about the midpoint of the
flap, and the third notch 214 is formed near the rim 206 of the
flap. The second and third notches 212 and 214 further increases
the flexibility of the flap, thereby further reducing the downward
load on the substrate transmitted through the flexible membrane. Of
course, implementations are possible with two notches, or four or
more notches.
[0033] Referring to FIG. 4A, in another implementation, the
flexible membrane 140c includes a main portion 142c and an outer
portion 220 with a triangular cross-section connected to the outer
edge of the main portion 142c. A lower surface 144 of the main
portion 142c provides a mounting surface for the substrate 10. The
three innermost annular flaps 150c, 152c and 154c are connected to
the main portion 142c of the flexible membrane 140c. The two
outermost annular flaps 156c and 158c are connected to the two
vertices of the triangular outer portion 220. Each membrane flap
150c, 152c, 154c, 156c and 158c includes a thick rim 222 that is
clamped between a clamp ring and the base, and a substantially
horizontal portion 224 extending radially away from the rim 222. In
the case of the two outermost annular flaps 156c and 158c, the
horizontal portion 224 connects directly to the triangular outer
portion 220. In the case of the three innermost annular flaps 150c,
152c and 154c, the horizontal portion 224 is connected to the main
portion 142c by a thick wedge-shaped portion 230, also with a
triangular cross-section. The wedge-shaped portion 230 can have
sloped face 232 on the same side of the flap as the rim 206, and a
generally vertical face 234 on the opposing side. In operation,
when one of the chambers is pressurized or evacuated, the
substantially horizontal portions 224 flex to permit the main
portion 142c to move up or down.
[0034] A potential advantage of this membrane configuration is
reduced resistance to vertical motion by different sections of the
main portion of the 142c of the flexible membrane 140c. Another
potential advantage of this membrane configuration is a uniform
pressure distribution at low applied pressures or when there are
uneven pressures in adjacent chambers. The wedge-shaped portion 230
generally prevents the membrane flap from bowing into the
low-pressure chamber, thereby reducing or eliminating compressions
in the main portion 142c that might result from bending of the
flap. In addition, the thick wedge-shaped portion 230 distributes
the downward load from the weight of the flap across a wide area on
the substrate, thereby improving uniformity at low pressures.
[0035] The two outer chambers 166c and 168c can be used to control
the pressure distribution on the outer perimeter of the substrate.
If the pressure P.sub.1 in the outermost chamber 168c is greater
than the pressure P.sub.2 in the second chamber 166c, the outer
portion 224 of the flexible membrane 140c is driven downwardly,
causing the lower vertex 226 he outer portion 224 to apply a load
to the outer edge of the substrate. On the other hand, as shown in
FIG. 4B, if the pressure P.sub.1 in the outermost chamber 168c is
less than the pressure P.sub.2 in the second chamber 166c, the
outer portion 224 pivots so that the lower vertex 226 is drawn
upwardly. This causes the outer edge of the main portion 142c to be
drawn upwardly and away from the perimeter portion of the
substrate, thereby reducing or eliminating the pressure applied on
this perimeter portion. By varying the relative pressures in the
chambers 166c and 168c, the radial width of the section of the
membrane pulled away from the substrate can also be varied. Thus,
both the outer diameter of the contact area between the membrane
and the substrate, and the pressure applied in that contact area,
can be controlled in this implementation of the carrier head.
[0036] The configurations of the various elements in the carrier
head, such as the relative sizes and spacings the retaining ring,
the base assembly, or the flaps in the flexible membrane are
illustrative and not limiting. The carrier head could be
constructed without a loading chamber, and the base assembly and
housing can be a single structure or assembly. The notches can be
formed in other locations, the different flaps may have different
numbers of notches, some of the flaps may be formed without
notches, and there can be one or more notches on the outermost
flap.
[0037] The present invention has been described in terms of a
number of embodiments. The invention, however, is not limited to
the embodiments depicted and described. Rather, the scope of the
invention is defined by the appended claims.
* * * * *